The present invention relates to preamplifiers for use in disk drives, and, more particularly, to the layout of attachment pads on the preamplifier used in attaching the preamplifier to a flex circuit for electrically connecting head cells in the preamplifier to the heads.
Preamplifiers have long been used in the manufacture of disk drives. The preamplifier chip is often fabricated as a separate component, and then placed into the disk drive for subsequent attachment via electrical connections to both upstream such as to a power supply and downstream such as to the read-write head. To facilitate electrical connection of the preamplifier chip, preamplifier chips typically have a number of metallic attachment pads or bond pads. Each bond pad provides a separate attachment location to an electrically conductive lead. For instance, in MR heads, each read-write head may require four separate electrical leads. The preamplifier chip may accordingly include four bond pads per head, for connection downstream to each of the leads for each head. The preamplifier chip may also include a number of leads for upstream connection, such as for voltage sources and outputs. The upstream leads are common for all of the heads, and are known as "control" leads.
Typically, preamplifier chips are rectangular and include control bond pads along one side. Bond pads along the remaining three sides are devoted to the head cells.
As disk drives become smaller and smaller, the real estate provided for the preamplifier chip is at an increasing premium. It is desired to make the preamplifier chip as small as possible, while still permitting enough space for bond pads to all of the necessary inputs and outputs. Space constraints are particularly important as the number of heads used in the disk drive and driven by the preamplifier chip increases. For instance, if four bond pads are used for each head, a four-head (two disks) circuit requires only sixteen pads devoted for the head cells. A twelve head arrangement (six disks) requires forty-eight pads for the head cells to be driven by a single preamplifier chip.
As the number of disks/heads in a disk drive increases and as size decreases, the placement of the bond pads on the preamplifier chip becomes increasingly important. Better designs and systems for attaching a preamplifier circuit within a disk drive are needed.